<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div class="test">
        <div class="box"></div>
    </div>
</body>
<style lang="less">
    .test{
        display: flex;
        justify-content: center;
        align-items: center;
    }
    .box{
        width: 80%;
        height: 700px;
        background-color: bisque;
    }
    .box::after{
        position: absolute;
        content: "";
        width: 100%;
        height: 100%;
        /* left: 0px;
        right: 0px;
        top: 0px;
        bottom: 0px; */
        background-color: black;
        /* background-size: 100% 100%; */
        /* box-shadow: ; */
    }
</style>
</html>